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Plate Tectonics Earth structure: Core: inner core solid (iron) outer core liquid (iron) Mantle: composed of Fe/Mg- rich silicates (olivine, pyroxene) Crust: continental – 20–90 km thick (old) Ocean crust- 5–10 km thick (young) Lithosphere: crust + upper mantle = “Plates” Asthenosphere: partially molten upper mantle Mantle: convection due to radioactive heating 3 types of plate boundary; Convergent : compression stress Divergent: tensional stress Transform: shearing stress Passive continental margin: E. coast USA Active margin: W. coast USA; W. coast S. America Hot spots: within plate e.g. Hawaiian chain Supercontinents : Pangaea (breakup 200 m.y. ago), Rodinia (breakup 600 my ago) Wilson cycle: opening and closing of ocean basins Rock cycle can be understood in context of plate tectonics Modification of plate tectonic theory: Terrane accretion